Fluorescence imaging is a powerful and versatile tool for a variety of applications. For example, fluorescence imaging agents or fluorophores and their corresponding imaging systems have been used to visualize and/or analyze biological systems with high resolution. Organic dyes or fluorophores are perhaps the most widely used and studied imaging agents, partly because their fluorescence mechanisms are well-understood by researchers. Other fluorescent probes have also been developed, including quantum dots (QD), green fluorescent proteins (GFP), graphene oxides (GO), and carbon dots (CD). However, some major fluorescence imaging agents used for imaging applications such as biomedical imaging applications suffer from one or more disadvantages, including photobleaching, short lifetimes, intrinsic toxicity, lack of biodegradability, and/or instability in vivo. In addition, some existing fluorescence imaging agents also provide relatively weak mechanical strength and/or robustness when incorporated into other material systems. Therefore, there exists a need for improved luminescent species, including for fluorescence imaging and sensing applications.